feat: unplan Week Ahead work with undo (Closes #1240)

frontend/index.html

@@ -526,6 +526,8 @@
       </section>
       <div class="week-review-duplicates" id="week-review-duplicates" role="alert" hidden></div>
       <div class="week-review-days" id="week-review-days"></div>
+      <div class="week-unplan-receipt" id="week-unplan-receipt" role="status" aria-live="polite" hidden></div>
+      <button id="undo-week-unplan" type="button" hidden>Undo</button>
       <div class="small week-review-status" id="week-review-status" role="status" aria-live="polite"></div>
       <button id="edit-week-plan" type="button" hidden>Edit week</button>
       <button id="confirm-week-plan" type="button">Confirm Week Ahead</button>